<template>
  <div>
    <p>请选择你要购买的书籍</p>
    <ul>
      <li v-for="(item, index) in arr" :key="index">
        {{ item.name }}
        <button @click="item.count++">买书</button>
      </li>
    </ul>
    <table border="1" width="500" cellspacing="0">
      <tr>
        <th>序号</th>
        <th>书名</th>
        <th>单价</th>
        <th>数量</th>
        <th>合计</th>
      </tr>
      <tr v-for="(item, index) in arr" :key="index">
        <th>{{ index + 1 }}</th>
        <th>{{ item.name }}</th>
        <th>{{ item.price }}</th>
        <th>{{ item.count }}</th>
        <th>{{ item.price * item.count }}</th>
      </tr>
    </table>
    <p>总价格为:{{ sum }}</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      arr: [
        {
          name: "水浒传",
          price: 107,
          count: 0,
        },
        {
          name: "西游记",
          price: 192,
          count: 0,
        },
        {
          name: "三国演义",
          price: 219,
          count: 0,
        },
        {
          name: "红楼梦",
          price: 178,
          count: 0,
        },
      ],
    };
  },
  computed: {
    sum: {
      get() {
        return this.arr.reduce((num, item) => {
          return num + item.price * item.count;
        }, 0);
      },
    },
  },

  /* watch: {
    arr: {
      handler(newData) {
        console.log(newData);
      },
      deep: true,
    },
    sum: {
      handler(newData) {
        console.log(newData);
      },
      deep: true,
    },
  }, */
};
</script>